As the industry has advanced, process variation in deep sub-micron chip manufacturing has become more and more significant. Process variation can cause more than a 30% variation in circuit performance, and cause even a larger power consumption variation. Presently, how process variation causes performance variation and power consumption variation is one of the most important problems in deep sub-micron chip making.
A large amount of time margins are usually added to the design flow to compensate for the delay fluctuation which is caused by process variation. However, this compensation method (i.e., adding time margins) can only ensure that the circuit will function. It does not compensate for power consumption variation. As such, process variation impacts performance and power consumption and typically performance and power consumption are not optimized.